Impact hammer element



was

.P. E. SCHMID IMPACT HAMMER ELEMENT Aug. 13, 1957 INVENTOR. Pau/ E. Jcbm/d J9 1 BY I 6 ATTORNEY Aug. 13, 1957 P. E. SCH-MID 0 I IMPACT- HAMMER ELEMENT Filed May 14, 1952 3 Sheets-Sheet 2 INVENTOR. I Paul E. \Schm/a 957 P. E. SCHMID IMPACT HAMMER ELEMENT Filed May 14, 1952 3 Sheets Sheet 3 ATTORNEY IMPACT HAMMER ELEMENT Paul E. Schmid, Houston, Tex., assignor to Reed Roller Bit Company, Houston, Tex., a corporation of Texas Application May 14, 1952, Serial No. 287,717

2 Claims. (Cl. 19230.5)

This invention relates broadly to impact clutches and portable, rotary, reversible, pressure fluid actuated tools, such as wrenches, nut runners and the like, of the type shown and described in United States Letters Patent No. 2,580,631 dated January 1, 1952, to Edgar R. Whitledge, assigned to the assignee of the present application.

More specifically, this invention is an improvement of the impact hammer element shown and described in the copending application Serial No. 251,515, filed October 16, 1951, now Patent No. 2,663,395, and assigned to the assignee of the present application.

One of the principal objects of this invention is the provision of an impact clutch embodying details of construction shown and described in the aforesaid patent and copending application, but provided with nonparallel impacting faces, which have been found to produce a more efiicient tool having greater impact speed and torque output and capable of delivering a more uniform succession of impacts.

Other objects of this invention will be apparent from the following detailed description wherein similar characters of references designate corresponding parts and wherein:

Figure 1 is a side elevational view, with portions in section, approximately on the line 1-1 in Figure 3, of a hand tool embodying the present invention;

Figure 2 is a perspective view of a portion of the driving member of the impact clutch shown in Figure 1.

Figure 3 is a sectional view, approximately on the line 3--3 of Figure 1, showing a portion of the mechanism in neutral position.

Figures 4, 5, 6, 7 and 8 are views similar to Figure 3, but showing the parts in positions which they occupy successively during the cycle of operation.

Figure 9 is an enlarged view of the upper portion of Figure 5, and Figure 10 is a similar enlarged view of the upper portion of Figure 7.

As previously stated, this invention is directed to an impact clutch or impact wrench comprising a reversible motor designated generally by the reference character A, including a rotor 10, having radial vanes or blades 11 slidably supported within suitable grooves formed in the rotor and through the medium of which the rotor is drivenby pressure fluid, preferably compressed air, admitted thereto in a conventional manner by means including a trigger actuated valve, only the trigger 12 of which is shown in the drawings.

In addition to the motor already referred to, the tool comprises a driven member having a relatively small moment of inertia, a flywheel or driving member having a relatively large moment of inertia, and a simple, eflicient means for operatively connecting said members whereby the driving member is caused to successively impact the driven member. In the embodiment shown, the driven member is in the form of a shaft 13 rotatably supported in a bushing 14 fixedly secured in the forward end of a clutch housing 15 detachably connected to the motor housing 16 by screws, not shown. The reversibility of the driving means may be under the control of a sleeve-type "ice 2 reversing valve 17 for directing the pressure fluid to either peripheral extremity of the conventional, lunate, expansible chamber surrounding the rotor 10. The forward end of the shaft 13 is provided with a driving connection adapted to have an adapter, not shown, applied there to but which, in turn, is adapted to engage a nut, bolt; screw or other similar member which it is desired to tighten or remove. The rear or right-hand end of the shaft 13, as viewed in Fig. 1, is of slightly greater diameter and'is provided with two 'axially spaced, diametrically arranged, arcuately-shaped projections or anvils 18, 19 having radial sides 20, 21 adapted to be inpinged by impacting surfaces on plate-like impact or hammer members 22, 23 forming a part of the built-up flywheel or driving member or hammer assembly, designated generally by the reference character B. The anvils 18, 19 extend longitudinally of the shaft 13 and are impinged by the impact members 22, 23 respectively.

The improved impact members 22, 23 have a relatively large mass and are pivotally connected by pins 24; 25 to an integral cage, designated generally by the reference character 26. The pins 24, 25 are located diametrically opposite each other with respect to the axis of rotation of the driven member 13, which member is 'coaxially supported with respect to the driving or momentum member B and the rotor 10. The cage 26 comprises three spaced disks 27, 28 and 29 connected by relatively narrow webs 30, 31, 32 and 33 and the rear or right-hand end thereof, as viewed in Figs. 1 and 2, is keyed to the projecting spindle 34 of the rotor 10. The opposite or front end of the cage 26 is rotatably supported on the shaft 13 by a flanged bushing 35 of suitable wear-resisting material. Alternatively the cage may be of built-up construction.

The cage 26, as shown, is counterbored from the front end so as to permit the insertion of the anvil or rearend of the driven member 13. The impact members 22 and 23 are arranged axially with respect to each other in the cage 26, the impact member 22 being located intermediate the disk portions 27, 28 of the cage and the impact member 23 being located intermediate the disk portions 28, 29 of the cage. The pin 24 is fixedly secured in aligned apertures in the disks 27, 28 of the cage. The disk 29 is provided with apertures 36 counterbored from the front end of the cage to a distance equal to the thickness of the .disk 27 to form apertures as continuations of the apertures in the disks 27, 28 within one pair of which the pin 24 is located. The radial flange 38 on the bushing 35 which overlies a portion of the aperture within which the pin 24 is located prevents axial movement of the pin toward the front of the cage in the event the pin becomes loose in the cage and the impact member 23 which overliesthe' pin 24 prevents its movement in the opposite direction.

The impact members 22, 23 are similar in construction and the pin 25 is assembled in the cage 26 in a manner similar to that in which the pin 24 is assembled therein. The shoulder formed by the counterbore in the disk 29 within which the pin 25 is located prevents movement of the pin toward the rear in the event it becomes loose in the cage and the impact member 22 which overlies the pin prevents its movement toward the front. The counterbore in the disk 29 in alignment with the pin 24 merely facilitates assembly.

The impact members22, 23 are narrower than the distance between the webs 30, 31 and 32, 33, respectively, and the spaces between the disk-like portions27, 2 8 and 28, 29 within which the impact members are positioned are slightly greater than the thickness of the members 22, 23, with the result that the members 22, 23 are free to pivot between the Webs about-the pins 24, 25 respect-ivel'y. a

The improved impact members 22, 23 are alike, each being formed of flat stock resulting in two parallel end faces located between and in parallel relationship with the: disks .27- 28 or 2 8 -2 9. The one endof each impact member surrounding its pivotal connection with the. cagef26 forms a relatively large base portion 37, while the other end forms 'a smaller crown portion'39. The two portions are'joine'd by relatively long straight side walls 42, 43 having their edges beveled or chamfered to clear small radii existing between the webs and rings of the cage 26. Each web 30, 31, 32, 33 has an inner wall 44'forming a perfectly straight and flat surface of a width substantially equal to the thickness of the impact members 22, 23, the inner walls of the webs 30, 32 being diametrically opposed and parallel to the inner walls of the webs 31, 33 respectively. The symmetrical construction of the sides .42, 43 with respect to the pivotal 'axes of the impact members provides for reverse operation of the device, as will be hereinafter apparent.

The center of each impact member is'provided with an aperture 47 defined by 'arcuately-shaped, alternately arranged surfaces 48, 49, 50, 51 connected by straight impacting surfaces or shoulders 52, 53, 54, 55. The arcuately-shaped surfaces 48, 49 are of equal radii as are the surfaces 50,51 and all have their centers on a line passing through the center of the pivot pin 25 and the extreme end of the crown portion 39. The surfaces 50, 51 have a common center and the radii thereof are smaller than those of the surfaces 48, 49, the centers of which :a're'spaced apart to provide both the necessary clearance for the anvil 19 and to provide ample size for the shoulders 52, 53, 54 and 55. Although the radii of the surfaces 50, 51am smaller than the radii of the surfaces 48, 49, they are suflicient to permit the anvil associated therewith to rotate relative to the impact member when the member'is swung to one side or the other about its pivotal connection with the cage 26. The construction of the side walls 42, 43 and the straight sides 44 of the webs of the cage 26 with which they engage is such that the impact members may move a sufficient distance to cause the internal straight surfaces 52, 53, 54, 55 thereof to engage and disengage the external radial surfaces 20, 21 of the anvils 18, 19 with which they cooperate.

The operation of both impact members 22, 23 is alike, therefore, it will 'be sufficient to describe only the operation of the impact member 23. Assuming that the flywheel or momentum member B is rotating in a clockwise direction, as indicated by the arrow R,.the respective parts are shown inFig. 8 in a position which they may occupy shortly after impact between the shoulder or surface 52 of the impact member 23 with the surface or shoulder of theanvil 19. When the shoulder or surface 52 of the impact member struck or impacted the shoulder 20 of the anvil 19, see Fig. 7, the impact member 23 was rotated by the reaction produced, acting in the direction of the force arrow 60, in a clockwise direction about the pin until the side 42 struck the side 44 of the web 32. This movement of the impact member 23 allowed the shoulder 52 and the surface to pass around the anvil 19. As the shoulders 20, 52disengage, the flywheel proper accelerates. The center of mass of the impact member is preferably olfset with respect to the axis of rotation of the clutch proper and the inertia of the impact member causes it to tend to lag behind the cage 26.

As soon as the surface 50 passes the rear end of the anvil 19 defined by the radial surface 21, which it is about to do, as shown in Fig. 4, the impact member will be free to rotate in a counterclockwise direction about the pin 25. At this time the flywheel proper is accelerating and driving impact member 23 through pin25. The effect of inertia of the impact member 23, as previously mentioned, causes the member to lag behind the flywheel proper whereupon the impact member will move from a position with the side wall 42 in engagement with the web 32 shown in Fig. 4 to a position with the side wall 43 in engagement with the web 33. The parts then will be in the approximate position shown in Fig. 6 and the surface 52 again in position to impinge the surface 20 of the anvil 19.

The method of operation just described is automatic but being subject to frictional drag between the parts, it is not positive, and to insure proper setting up of the impact member for the primary impact, the impact member 23 is provided with the internal shoulder 54 which cooperates with the surface 20 on the anvil, if necessary, to assure proper resetting of the impact member. As shown in Fig. 4, the arcuately-shaped surface 50 is about to complete its passage over the anvil 19 and the shoulder 54 is approaching the impact surface 20 of the anvil and in the event the impact member 23 has not been reset by inertia, as explained before, and the side 43 not in engagement with the web 33, by the time the shoulder 54 reaches the shoulder 20, the shoulder 54 will impact or strike the shoulder 20, as indicated in Fig. 5. The anvil 19 will offer resistance to rotation of the flywheel proper and will act against the shoulder 54 to rotate the impact member in a counterclockwise direction about the pin 25 until the shoulder 43 strikes the web 33, as indicated in Fig. 6. V

The force exerted by the anvil 19 against the member 23 will act in the direction indicated by the force arrow 61 and will have a moment arm of magnitude 62 about the center of the pin 25. As the member 23 rotates about the pin 25, the shoulders 20, 54 will be disengaged and the arcuately-shaped surface 51 will be permitted to pass about the anvil 19,see Fig. 6, .whereupon the flywheel continues to rotate freely until impact is made between the surfaces or shoulders 20, 52, see Fig. 7. The condition existing when the shoulder 52 strikes the shoulder 20 is somewhat similar to that existing when the shoulder 54' strikes the shoulder 20 shown in Fig. 5, but the moment arm of the impact force about the center of the pin 25 is much shorter than the moment arm 62, with the result that the impact or blow delivered to the anvil 19 is considerably greater and has considerable force.

It will be noted that the power is transmitted to the impact member through the pivot pin 25 and that the shoulder 52 is adjacent to but trails the axis about which the impact member is pivoted to the driving member or flywheel proper. By varying the'radial position of the ivot with respect to the shoulder 52, etc., or by varying the angular position of the shoulder 52 with respect to the pivot, the moment arm 62 can be increased or decreased to vary the blow imparted to the anvil; The same is true of the shoulder 54 which, as shown, leadsthe pivot for the impact -member. When the shoulder 52 strikes the shoulder 20 of the anvil, the reaction produces a clockwise acceleration of the impact member23 about t the pin 25 which because of the relatively large mass of the impact member adds to the force of impact, moves the side wall 42 into engagement with the straight sur-' face 44 of the web 32, disengages the shoulders 20, 52 and permits'the flywheel to resume rotation about the anvil.

Referring now more particularly to the invention, from the foregoing description it will be understood that during rotation of the impact members in one direction, the straight shoulders 52, 54 are engageable with the anvil straight sides 20, 'andthe straight shoulders 53, 55 with the straight sides 21 upon rotation of the impact members in the other direction. Heretofore, these impacting faces, that'is, shoulders 52 or 54 and'sides 20 as well as shoulders 53 or 55 and;sides 21, weie arranged and disposed in a manner causing them to be parallel or'substantially parallel at the moment 'of impact." Tothat end, the sides 20,21 of'the ,anvils .18, l9'w'ere made radial with respect to the center axis of the anvil shaft 13, while.

the shoulders ofthe impact elements-were of angles calculated to bring them parallel to the sides 20, 21 at the moment of impact. It did appear that the provision of parallel impact faces at the moment of impact, was not only the obvious way to construct the anvils and impact elements, but from an engineering point of view it was believed to result in the best performance and maximum efficiency of the impact mechanism. However, as a result of further experiments, it was discovered that by changing the angles of the shoulders 52, 53, 54, and 55in a manner causing them to be non-parallel with the sides 20, 21 at the moment of impact, the impact speed of the tool was increased to a marked degree. Furthermore, it was also noted that the succession of impacts were delivered in a more uniform manner, that the tool ran smoother during impact delivery and as a whole became more efiicient than tools having parallel impact surfaces at the moment of impact.

Optimum conditions have been found to exist with the impacting faces, at the moment of impact, at an angle of about 16, and as shown plainly in Figs. 9 and 10, with the shoulders 'or driving faces such as 52 of the impact element, diverging from the outer end of the anvil driven faces such as 20 outwardly toward the inner end 70 thereof. In other words, it is the bottom ends, preferably rounded as at 71, of the impact elements driving faces, which impinge upon the outer ends, also rounded as at 72, of the anvils driven faces 20 and 21. As clearly shown,

the rounded or concaved bottom end 71 of each driving face of the impact element is of a substantially greater radius than that of the rounded or convexed outer end 72 of each driven face of the anvil, thereby causing the area of engagement between the hammer element and the anvil at the time of impact to be limited to a fraction of the surface area of the convexed outer end aforesaid. In this improved construction, the straight faces 20, 21 of each anvil are preferably radial with respect to the axis of rotation of the shaft 13, While the resetting shoulders 54, 55 of the impact elements are parallel to each other and to the horizontal center line of each impact element passing through the center axis of its pivot 25.

Since the anvils 18, 19 and the pivots for the impact elements 22, 23 are offset 180 degrees, two power blows or impacts which act as a couple are effected upon each rotation of the flywheel assembly B. Obviously any number of impact members and anvils may be employed, in which event any desired number of impacts will be obtained for each rotation of the flywheel.

The anvils 18, 19 and the impact members 22, 23 are symmetrical with respect to a central plane, from which it follows that the clutch or operative connection between the driving member B and the driven member 13 is reversible, therefore, it is only necessary to employ a reversible motor and the tool is suitable for tightening or loosening nuts, bolts, screws and the like. Referring to the operation of the impact member 23, when the drive is reversed the shoulders 21, 53 and 55 correspond with the shoulders 20, 52 and 54, respectively.

I claim:

1. An impact driving connection comprising a rotatably supported driven member, a rotatable driving member coaxially supported with respect to said driven member, a cylindrical hammer carrier between said members connected to said driving member for rotation therewith, a pair of axially spaced diametrically opposed anvils on said driven member and within said carrier having radial straight faces formed with convexed outer ends furtherest from the center axis of said driven member, a hollow hammer element surrounding each anvil and pivotally connected to said carrier for rotation therewith and pivotal movement relative thereto, each hammer element having an internal concaved shoulder movable into and out of the path of its respective anvil by virtue of said pivotal movement for delivering a succession of impacts to one of said anvil outer convexed ends and effecting step by step rotary motion of said driven member, the radius of said concaved shoulder being substantially greater than the radii of said convexed outer ends thereby causing the area of engagement between each hammer element and its respective anvil at the time of impact to be limited to a fraction of the surface area of each of said convexed outer ends.

2. An impact driving connection comprising a rotatably supported driven member, a rotatable driving member coaxially supported with respect to said driven member, a cylindrical hammer carrier between said members connected to said driving member for rotation therewith, a painof axially spaced diametrically opposed anvils on said driven member and within said carrier having impact receiving convexed outer faces furtherest from the center axis of said driven member, a hollow hammer element surrounding each anvil and pivotally connected to said carrier for rotation therewith and pivotal movement relative thereto, each hammer element having an internal concaved shoulder movable into and out of the path of its respective anvil by virtue of said pivotal movement in exclusive engagement with one of said anvil convexed outer faces for delivering a succession of impacts thereto effecting step by step rotary motion of said driven member, the radius of said concave shoulder being substantially greater than the radii of said convexed outer faces thereby causing the area of engagement between each hammer element and its respective anvil at the time of impact to be limited to a fraction of the surface area of each of said convexed outer faces.

References Cited in the file of this patent UNITED STATES PATENTS 2,225,698 Hutchinson Dec. 24, 1940 2,508,997 Fitch May 23, 1950 2,514,914 Van Sittert July 11, 1950 2,580,031 Whitledge Ian. 1, 1952 2,663,395 Schmid Dec. 22, 1953 

